Miniature ureteroscope distal tip designs for potential use in thulium fiber laser lithotripsy

Abstract

Thulium fiber laser lithotripsy using smaller optical fibers may enable development of miniature ureteroscopes. Two ureteroscope distal tip prototypes were built and characterized. The first design was 4.5-French (Fr) [1.5-mm outer diameter (OD)], five channel tip, housing 200-μm inner diameter (ID) dedicated central channel for insertion of 100-μm core fibers and four surrounding channels, each with 1.5 Fr (510-μm ID) for instrumentation, irrigation, imaging, and illumination, respectively. The second design was 6.0-Fr (2.0-mm OD), three-dimensional printed tip with larger, hemispherical common working channel and separate detection port integrated with ring lighting. Standard instruments, including optical fibers, guidewires, and stone baskets, were inserted through working channels to demonstrate feasibility. Gravitational and manual pump-assisted saline irrigation rates were measured. Luminous intensity distribution curves (LIDCs) were modeled for both ring and conventional lighting designs. Imaging was conducted using 3000, 6000, and 10,000 pixel, miniature, flexible endoscopes with 0.4-, 0.6-, and 0.9-mm OD, to differentiate between urinary stones and ureter wall, for potential clinical application. The multichannel ureteroscope tip with 1.5-Fr working channel yielded a gravitational saline flow rate of 3.9 ± 0.2 mL / min compared to 31.3 ± 0.6 mL / min for standard (3.6 Fr) ureteroscope channel. Manual, pump-assisted irrigation increased flow rate to 32.5 ± 3.0 mL / min. The 6000 pixel, 0.6-mm OD, flexible endoscope provided a balance of clear differentiation between stones and ureter wall and sufficiently small OD. A ring lighting configuration provided more uniform illumination than conventional cross-lighting geometry as demonstrated by LIDCs. With further development, these miniature ureteroscope tip designs may be integrated into a fully functional ureteroscope to permit ureteral access with minimal trauma and improved patient safety and comfort.

Thulium fiber laser: the new player for kidney stone treatment? A comparison with Holmium:YAG laser

“…Prior studies on ureteroscopic Holmium laser lithotripsy have shown multiple advantages in favor of smaller laser fibers: better irrigation flow, better instrument deflection, and less stone retropulsion [46][47][48][49]. Another major potential advantage in favor of smaller fibers would be the possibility to reduce the working channel diameter of ureteroscopes, thus allowing for a major overall instrument miniaturization [50]. This would increase the space available between the ureteroscope and the ureter or access sheath, thus increasing irrigation outflow.…”

Urinary stone ablation with a thulium fibre laser: a rate-of-completion evaluation

“…При измерении скорости абляции контролируемыми параметрами при выполнении процедуры дробления во всех исследованиях являлись энергия лазерных импульсов Ei и частота их следования Fi. Одни исследователи ограничивались только этими двумя параметрами [5,11,13], другие учитывали также длительность лазерных импульсов ti и диаметр оптического волокна [10,14,16]. При проведении тулиевой литотрипсии в одних случаях использовались тулиевые волоконные лазеры с длиной волны 1940 нм, а в других 1908 нм.…”

Recent advances in infrared laser lithotripsy [Invited]

“…Smaller fibers may also spur development of incrementally smaller instruments for use in ureteroscopy (e.g. integrated fiber/basket and miniature ureteroscopes) [ 99 , 100 ]. Given that engineers designing newer and progressively smaller endoscopes may devote significant time and effort attempting to reduce the endoscope outer diameter by increments as small as 50 µm, use of these smaller fiber outer diameters may enable them to more easily achieve such milestones [ 101 ].…”